by Tim Momol and Prakash Pradhanang

Contact:
Dr. Timur (Tim) Momol
Extension Plant Pathologist
Assistant Professor of Plant Pathology
University of Florida, IFAS, NFREC, and Plant Pathology Department
155 Research Road
Quincy, FL 32351, USA

Tel: 850-875-7154
Suncom: 294-7154
Fax: 850-875-7148
(850) 875-7154
tmomol@ufl.edu

During the fall season of 2001, the Florida Extension Plant Diagnostic Clinic-Quincy received 'Patriot Cherry' and 'Patriot Bright Red' geranium plants (Pelargonium x hortorum) from an ornamental plant producer in Florida. The leaves were wilted and chlorotic (Fig. below) and the stem base and roots were rotted. When cross sections of the stem base were placed in a tube of clear water, white milky strands of bacterial cells were visible. A group of scientists (Prakash Pradhanang, Tim Momol, Hank Dankers, Esen Momol and Jeff Jones), from UF/IFAS, NFREC and Plant Pathology Department, identified the causal agent as Ralstonia solanacearum. Wilt pathogen was consistently isolated from the stem bases when plated on semiselective media. Identification of presumptive R. solanacearum strains was confirmed by whole-cell fatty acid methyl ester analysis (MIDI) and by polymerase chain reaction (PCR).

The ornamental plant producer was visited to assess the intensity of the disease. Several benches of diseased geraniums were observed. All sanitation procedures were applied and a total of 60,000 geraniums were destroyed to prevent further infections in the production areas. The total loss was estimated at $80,000.

Southern wilt of geranium was reported in North Carolina in 1981, but the biovar was not identified. To our knowledge, this is the first report of R. solanacearum causing Southern wilt in geranium in Florida. We have established that the pathogen in this case was biovar 1 which is commonly found in the southern United States and South America.

See additional symptoms (314 KB PDF).

Reference site from Internet: http://ibws.nexenservices.com/